How would you make your city better?

A defining issue of the 21st century is how to build smarter and more liveable urban areas

We want to know what one thing you would want to change in your city

"The City" is a CNN special series that profiles the sustainable urban future of five cities over five days. Watch the show every day during our special theme week starting Monday, Aug 19 on "World Business Today" at 1300 GMT and "Connect The World" at 2000 GMT.

(CNN) -- With more than half of the world's population expected to live in cities by 2050, there's never been a more important time for urban dwellers to shape their city's sustainable future.

In CNN's "The City", we take a look at the world's different urban hubs and their visions for a greener future. Initiatives include everything from floating pavilions in Rotterdam to car-free days in Seoul.

Now we want to know what improvements you'd like to make to your city. What one thing would you want to change to make it smarter, greener and more sustainable?

Tell us in the comment section below or via the hashtag #MyCityWish on Twitter, Facebook or Instagram. It can be absolutely anything, from more cycling lanes to bee hives on every rooftop.

Take us to your city and tell us your wish, in video, photograph along with a short description via Instagram, Instavideo or Vine.